bpo-20104: Change the file_actions parameter of os.posix_spawn(). (GH-6725)

* Make its default value an empty tuple instead of None.
* Make it a keyword-only parameter.

4 files changed, 41 insertions, 40 deletions

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index b8d6fffb30..bc8d5a8abb 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -3394,7 +3394,7 @@ written in Python, such as a mail server's external command delivery program.
    subprocesses.
 
 
-.. function:: posix_spawn(path, argv, env, file_actions=None, /, *, \
+.. function:: posix_spawn(path, argv, env, *, file_actions=None, \
                           setpgroup=None, resetids=False, setsigmask=(), \
                           setsigdef=(), scheduler=None)
 
@@ -3402,7 +3402,8 @@ written in Python, such as a mail server's external command delivery program.
 
    Most users should use :func:`subprocess.run` instead of :func:`posix_spawn`.
 
-   The *path*, *args*, and *env* arguments are similar to :func:`execve`.
+   The positional-only arguments *path*, *args*, and *env* are similar to
+   :func:`execve`.
 
    The *file_actions* argument may be a sequence of tuples describing actions
    to take on specific file descriptors in the child process between the C
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index dafe9c1350..7a2fc263cb 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1499,8 +1499,7 @@ class TestPosixSpawn(unittest.TestCase):
                 pidfile.write(str(os.getpid()))
             """
         args = self.python_args('-c', script)
-        pid = posix.posix_spawn(args[0], args,
-                                os.environ)
+        pid = posix.posix_spawn(args[0], args, os.environ)
         self.assertEqual(os.waitpid(pid, 0), (pid, 0))
         with open(pidfile) as f:
             self.assertEqual(f.read(), str(pid))
@@ -1538,7 +1537,7 @@ class TestPosixSpawn(unittest.TestCase):
             self.NOOP_PROGRAM[0],
             self.NOOP_PROGRAM,
             os.environ,
-            []
+            file_actions=[]
         )
         self.assertEqual(os.waitpid(pid, 0), (pid, 0))
 
@@ -1691,37 +1690,38 @@ class TestPosixSpawn(unittest.TestCase):
         ]
         pid = posix.posix_spawn(self.NOOP_PROGRAM[0],
                                 self.NOOP_PROGRAM,
-                                os.environ, file_actions)
+                                os.environ,
+                                file_actions=file_actions)
         self.assertEqual(os.waitpid(pid, 0), (pid, 0))
 
     def test_bad_file_actions(self):
         args = self.NOOP_PROGRAM
         with self.assertRaises(TypeError):
-            posix.posix_spawn(args[0], args,
-                              os.environ, [None])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[None])
         with self.assertRaises(TypeError):
-            posix.posix_spawn(args[0], args,
-                              os.environ, [()])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[()])
         with self.assertRaises(TypeError):
-            posix.posix_spawn(args[0], args,
-                              os.environ, [(None,)])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[(None,)])
         with self.assertRaises(TypeError):
-            posix.posix_spawn(args[0], args,
-                              os.environ, [(12345,)])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[(12345,)])
         with self.assertRaises(TypeError):
-            posix.posix_spawn(args[0], args,
-                              os.environ, [(os.POSIX_SPAWN_CLOSE,)])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[(os.POSIX_SPAWN_CLOSE,)])
         with self.assertRaises(TypeError):
-            posix.posix_spawn(args[0], args,
-                              os.environ, [(os.POSIX_SPAWN_CLOSE, 1, 2)])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[(os.POSIX_SPAWN_CLOSE, 1, 2)])
         with self.assertRaises(TypeError):
-            posix.posix_spawn(args[0], args,
-                              os.environ, [(os.POSIX_SPAWN_CLOSE, None)])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[(os.POSIX_SPAWN_CLOSE, None)])
         with self.assertRaises(ValueError):
-            posix.posix_spawn(args[0], args,
-                              os.environ,
-                              [(os.POSIX_SPAWN_OPEN, 3, __file__ + '\0',
-                                os.O_RDONLY, 0)])
+            posix.posix_spawn(args[0], args, os.environ,
+                              file_actions=[(os.POSIX_SPAWN_OPEN,
+                                             3, __file__ + '\0',
+                                             os.O_RDONLY, 0)])
 
     def test_open_file(self):
         outfile = support.TESTFN
@@ -1736,8 +1736,8 @@ class TestPosixSpawn(unittest.TestCase):
                 stat.S_IRUSR | stat.S_IWUSR),
         ]
         args = self.python_args('-c', script)
-        pid = posix.posix_spawn(args[0], args,
-                                os.environ, file_actions)
+        pid = posix.posix_spawn(args[0], args, os.environ,
+                                file_actions=file_actions)
         self.assertEqual(os.waitpid(pid, 0), (pid, 0))
         with open(outfile) as f:
             self.assertEqual(f.read(), 'hello')
@@ -1754,9 +1754,8 @@ class TestPosixSpawn(unittest.TestCase):
                     closefile.write('is closed %d' % e.errno)
             """
         args = self.python_args('-c', script)
-        pid = posix.posix_spawn(args[0], args,
-                                os.environ,
-                                [(os.POSIX_SPAWN_CLOSE, 0),])
+        pid = posix.posix_spawn(args[0], args, os.environ,
+                                file_actions=[(os.POSIX_SPAWN_CLOSE, 0),])
         self.assertEqual(os.waitpid(pid, 0), (pid, 0))
         with open(closefile) as f:
             self.assertEqual(f.read(), 'is closed %d' % errno.EBADF)
@@ -1773,8 +1772,8 @@ class TestPosixSpawn(unittest.TestCase):
                 (os.POSIX_SPAWN_DUP2, childfile.fileno(), 1),
             ]
             args = self.python_args('-c', script)
-            pid = posix.posix_spawn(args[0], args,
-                                    os.environ, file_actions)
+            pid = posix.posix_spawn(args[0], args, os.environ,
+                                    file_actions=file_actions)
             self.assertEqual(os.waitpid(pid, 0), (pid, 0))
         with open(dupfile) as f:
             self.assertEqual(f.read(), 'hello')
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index f7767c4af0..c3849a93c0 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -1730,7 +1730,7 @@ exit:
 #if defined(HAVE_POSIX_SPAWN)
 
 PyDoc_STRVAR(os_posix_spawn__doc__,
-"posix_spawn($module, path, argv, env, file_actions=None, /, *,\n"
+"posix_spawn($module, path, argv, env, /, *, file_actions=(),\n"
 "            setpgroup=None, resetids=False, setsigmask=(),\n"
 "            setsigdef=(), scheduler=None)\n"
 "--\n"
@@ -1769,12 +1769,12 @@ static PyObject *
 os_posix_spawn(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
 {
     PyObject *return_value = NULL;
-    static const char * const _keywords[] = {"", "", "", "", "setpgroup", "resetids", "setsigmask", "setsigdef", "scheduler", NULL};
-    static _PyArg_Parser _parser = {"O&OO|O$OiOOO:posix_spawn", _keywords, 0};
+    static const char * const _keywords[] = {"", "", "", "file_actions", "setpgroup", "resetids", "setsigmask", "setsigdef", "scheduler", NULL};
+    static _PyArg_Parser _parser = {"O&OO|$OOiOOO:posix_spawn", _keywords, 0};
     path_t path = PATH_T_INITIALIZE("posix_spawn", "path", 0, 0);
     PyObject *argv;
     PyObject *env;
-    PyObject *file_actions = Py_None;
+    PyObject *file_actions = NULL;
     PyObject *setpgroup = NULL;
     int resetids = 0;
     PyObject *setsigmask = NULL;
@@ -6648,4 +6648,4 @@ exit:
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=ef78384ae88712e1 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=758ee0434fb03d90 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 4a8a8d70ae..c5d9a17b00 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5405,10 +5405,10 @@ os.posix_spawn
         Tuple or list of strings.
     env: object
         Dictionary of strings mapping to strings.
-    file_actions: object = None
-        A sequence of file action tuples.
     /
     *
+    file_actions: object(c_default='NULL') = ()
+        A sequence of file action tuples.
     setpgroup: object = NULL
         The pgroup to use with the POSIX_SPAWN_SETPGROUP flag.
     resetids: bool(accept={int}) = False
@@ -5419,6 +5419,7 @@ os.posix_spawn
         The sigmask to use with the POSIX_SPAWN_SETSIGDEF flag.
     scheduler: object = NULL
         A tuple with the scheduler policy (optional) and parameters.
+
 Execute the program specified by path in a new process.
 [clinic start generated code]*/
 
@@ -5427,7 +5428,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
                     PyObject *env, PyObject *file_actions,
                     PyObject *setpgroup, int resetids, PyObject *setsigmask,
                     PyObject *setsigdef, PyObject *scheduler)
-/*[clinic end generated code: output=45dfa4c515d09f2c input=2d7a7578430a90f0]*/
+/*[clinic end generated code: output=45dfa4c515d09f2c input=2891c2f1d457e39b]*/
 {
     EXECV_CHAR **argvlist = NULL;
     EXECV_CHAR **envlist = NULL;
@@ -5477,7 +5478,7 @@ os_posix_spawn_impl(PyObject *module, path_t *path, PyObject *argv,
         goto exit;
     }
 
-    if (file_actions != Py_None) {
+    if (file_actions != NULL) {
         /* There is a bug in old versions of glibc that makes some of the
          * helper functions for manipulating file actions not copy the provided
          * buffers. The problem is that posix_spawn_file_actions_addopen does not